Centralized traffic controlling system for railroads



Dec. 26, 1939'. 2,184,696

f CENTRALIZED TRAFFIC CONTROLLING. SYSTEM FOR RAILROADS D. HAILES 4 Shets-Sheet 1 Filed May 7, 1937 w. D. HAILES Dec. 26, 1939.

CBNTRALIZED TRAFFIC CONTROLLING SYSTEM FOR RA'ILROADS 4 Sheds-Sheet 2 Filed May '7, 1937 v. m 3!- J W. D. HAILES Filed May 7. 1957 4 Sheets-Sheet :5

CENTRALIZED TRAFFIC CONTROLLING SYSTEM FOR RAILROADS I Ni m h n .r a: F L. l- A mfll j 3 w: m: Y I I m w .W. a u m I JTQA A u A n A u m o. .cou+ 1 a: x i om T12 u 8 3d oi p q E E on on E 3 mm 5 5.8. m 82 N. Em 3 n Dec. 26, 1939.

Dec. 26, 1939.

w. D. HAILES CENTRALIZED TRAFFIC CONTROLLING SYSTEM'EOR RAILROADS Filed May 7, 1957 4 Shegts-Sheet 4 INVEN 0% 71/. @kv

Patented Dec. 26, 1939 7 CENTRALIZED TRAFFIC CONTROLLING SYSTEM FOR RAILROADS William D. Hailes, Brighton, N. Y., assignorto General Railway Signal Company, Rochester,

Application May 7, 1937, Serial No. 141,322

11 Claims.

This invention relates to centralized traffic controlling systems for governing traffic on railroads and it more particularly pertains to the communication part of such systems.

In a centralized trafiic controlling system oi" the type contemplated by this invention, the switch and signals are distributed at field stations throughout the territory and are governed from-the control ofiice by means of the transmission of controls over a two-wire line circuit interconnecting: the control oflice with the several field stations. Indications relating to the condition of the switches and signals, as well as track occupancy and unoccupancy, are trans mitted over the same two-wire line circuit to the control ofiice.

The two line wires connecting the control ofiice with all of the field station's comprise a single circuit, which serves the purpose of carrying the impulses used to select the required station and for transmitting controls to the selected station. This single circuit also serves to carry the indication impulses from a transmitting station to the control cities for registering a calling station in the ofiice and for transmitting indications from the registered station to the indication signal devices in the office.

. The present system is of the station selection coded duplex type, that is, it is operated through cycles of operation for the transmission of controls and/or the transmission of indications dur ing each cycle. When controls are transmitted, a station selecting code is first applied to the line circuit for selecting the desired station and then the controls are transmitted thereto by means of additional coded impulses. When indications are transmitted, the particular field station which is transmitting first transmits a station registering code for registrating or identifying this particular station in the control office and then the indications fromthe registered or identified station are transmitted to the control office by means of additional coded impulses.

For the transmission of controls, a predetermined number of impulses of selected polarities are placed on the line circuit for operating the apparatus in the control office and at the field circuit during a portion of each time space between the impulses which are applied to the line circuit from the control office. During a cycle for the transmission of indications, the'impulser at the transmitting field station provides the in- 6 dication code by inserting positive, negative or zero impulses. in between the stepping impulses applied to the line circuit in the control office during such a cycle. 1

One important feature of the present invention resides in the manner in which indication impulses are sandwiched in between the control impulses,'with these indication impulses being of distinctive polarity or being absent entirely. By

such an arrangement, the line circuit may be 15 coded at each step of the system in any one of three ways for transmitting one of a choice of three indications per step.

Another feature of the present invention resides in the manner in which the apparatus functions for the transmission of controls by means of polar impulses applied to the line circuit, in

i the same cycle during which this line circuit is used for the transmission of indications by means of polar impulses.

Still another feature of the present invention resides in the manner in which the indication impulser is inserted in the line at thetransmitting field station, during the time spaces between impulses applied to the line in thecontrol office,

' These characteristic features of the present invention, thus briefly stated, and other features of the present embodiment will be explained more in detail in the following description of one arrangement for carrying out the features of the invention, while various other characteristic features, functions and advantages of a system embodying this invention will be in part pointed out and part apparent as the description progresses.

In describing the invention in detail, reference will be made to the accompanying drawings, in

which those parts having similar features and i functions are designated throughout the drawings by like letter reference characters, which are generally made distinctive either by reason of distinctive exponents representative of their location in the system, or by means of preceding numerals representative of their order of operation during a cycle and in which:

Figs. 1A and 13 (with Fig. 1B placed below Fig. 1A) illustrate the apparatus and circuit arrangement employed at the control ofiice for providing means whereby the operator may select the stations and govern the switches and signals at the selected stations; and also for providing means whereby indications may be received from the various field stations throughout the territory.

Figs. 2A and 2B (with Fig. 2B placed below Fig. 2A) illustrate the apparatus and circuit arrangement employed at a typical field station for receiving the polar control impulses which are applied to the line circuit, for causing the station stepping mechanism to operate in synchronism with the office stepping mechanism and for providing the control code combinations. Figs. 2A and 23 also illustrate the apparatus and circuit arrangement employed at the field station for providing for the transmission of indications to the control office.

For the purpose of simplifying the drawings and facilitating in the explanation, various parts and circuits have been shown diagrammatically and certain conventional illustrations have been employed. The drawings have been, made more for the purpose of making it easy to understand the operation of the system, rather than with the idea of illustrating the specific arrangement that would preferably be employed in practice. For example, the various relays and their contacts are illustrated in a conventional manner and symbols are used to indicate the connections to the terminals of batteries or other source of current instead of showing all of the wiring connections to these terminals. Certain relays are shown on certain drawings in dotted blocks connected to the full line blocks, to indicate that the relays illustrated by the dotted line blocks are the same relays illustrated by the full line blocks appearing on some other drawing.

The symbols and are employed to indicate the positive and negative terminals respectively of suitable batteries or other sources of current and the circuits with which these symbols are used always having current flowing in the same direction, that is, from to The detailed circuits for operating the stepping relays in the control ofilce and at the illustrated field station have been omitted for the sake of simplicity, with dotted line connection 20 in Fig. 1A and dotted line connection 120 in Fig. 2A indicating that the stepping relay banks are controlled by contacts on the FF and SB relays. In the following description it will merely be mentioned that the stepping relays pick up and release during certain impulse and time space periods, and for an understanding of the detailed circuits for eifecting this operation of the stepping relay banks, reference may be had to Powell Patent, No. 2,058,824, issued October 27, 1936, which pa ,ent shows the control of similar stepping relays by contacts on the FF and SAP relays, the latter corresponding to relay SE of the present disclosure.

Furthermore, the method of station selection by means of the polar impulses applied to the control line from the control ofiice is not illustrated in detail, since this is accomplished by means of the SO relays at the stations (such as relay S0 of Fig. 2A) in the same manner as disclosed in Fig. 3 of the T. J. Judge et a1. application, Ser. No. 640,062, filed October 28, 1932, now Patent No. 2,082,544, granted June 1, 1937.

The detailed circuit arrangement and operation of the present system may be more readily understood by considering the drawings, with Fig. 2A placed to the right of Fig. 1A and with Figs. 13 and 2B placed in positions above mentioned, with correspondingly numbered lines in alignment.

Control ofiice equipment.The control ofiice includes a control machine having a group of control levers for each field station, a miniature track layout corresponding to the actual track I layout in the field and various indicating lamps,

or the like, together with the apparatus and circuits to accomplish the desired functions of the system.

For example, the apparatus for one track switch is illustrated as comprising switch machine lever SML (see Fig. 1A), starting or station button STB and code jumpers i3 and 14, together with the apparatus and circuits to accomplish the desired functions of the system. Since it is well known how the miniature track layout is arranged and how the various control levers are associated with the control office equipment, the major portion of this apparatus has been omitted, it only being deemed necessary to illustrate two code jumpers and a switch machine lever, since other control levers effect the transmission of controls in a manner similar to that which will be described for lever SML.

The system is started into a cycle of operations from the control ofiice by the momentary actuation of button STB, which effects the picking up of relays C and CD as indicated by means of dotted line H. The detailed circuits for accomplishing this function may be as disclosed in detail in the above mentioned Judge et al. application and consequently it is not believed necessary to morethan mention that relays C and CD are picked up at the beginning of a cycle, in response to the operation of button STB, when controls are to be transmitted during such cycle.

A neutral line relay F and a polar line relay R are provided in the control office and alternately inserted in the line circuit forpurposes which will be explained in detail. Resistance DR is a compensating resistance for maintaining the resistance in the line substantially constant irrespective of whether relay F is picked up or not. Repeating relay FP repeats the impulses applied to the line circuit from the control oflice, this relay following the operations of line relay F during each cycle of operations. Slow acting relays SA and SB are provided for defining the bounds of an operating cycle, that is, these relays are picked up in sequence at the beginning of a cycle, are held up by the impulses during this cycle and are then dropped out during the clearing out period at the end of the cycle.

Associated with the line and line repeating relays is a bank of stepping relays, comprising half step relay VP and stepping relays IV, 2V and 3V. Impulse controlling relay E serves to. control the beginning and the end of each impulse period, this relay being operated in response to the stepby-step operations of the stepping relay bank and in turn controlling the energization and deenergization of the line circuit by picking up and dropping the selected code sending relay PC or NO, these latter relays serving to apply positive or negative impulses respectively to the line circult.

Relay 0C is picked up at the beginning of each cycle of operations and is maintained energized th oughout the cycle, as long as relay E continues to function to provide impulses in the line circuit. If relay E remains down, for any reason, for too long a period, then relay 0C is dropped out and the control circuit including its lower front contact, which controls the PC and NC relays, is opened so that the system is restored to normal.

Relay CF is the station start relay, this relay being picked up when the system is initiated fromfield station and remains up throughout the following cycle, being dropped during the clearing out period at the end of the cycle. It is not believed necessary to illustrate the control of relay CF, it being suflicient to understand. that it is picked up when relay F is dropped in response to a station opening the line, the circuit for relay CF including back contact id of relay F.

Message receiving relays PM and NM register the positive and negative indication impulses received relay R during the time spaces between impulses applied to the line from the control omce. These message relays, when picked up, stuck up until the messages which they have received executed, by energizing indication receiving HR and 21R, in the manner n will described in detail in connection he description relating to the transmission cepticn of indications. station equipment.

The field station illustrated in. Figs. 2A and 2B is typical of all stations of the system and may be adapted for use at any location by merely connecting certain code to for the desired codes, but convenience in the description it is assumed this is the first station on the line by reason oi the distinctive exponents employed.

The track switch, switch machine, switch machine control relay, signals and signal control relays re not shown on the drawings, since the method oi controlling the track switch and signals by polar impulses applied to the line circuit is immaterial to an understanding of the present inve "on and may be the same as disclosed in abovementioned Judge et al., Patent No.

granted June 1, 1937.

The track section is likewise not illustrated, but for the purpose of illustrating the transmission of indications, relay WP is shown in Fig. 213, t"'" being the relay which repeats the position of the associated track switch by opening its neutral front contact when the rack switch is unlocked, by closing the neutral front contact and pcsiti ng the polar contact to the left when the canon is in its normal locked position, and by closing the neutral front contact and positioning its polar contact to the right when the switch reverse locked position.

e commmiicaticn part of the system, to the present invention is more closely ted, includes a line relay F of the three-position biased tomeutral polar type, together with its quiet; acting repeating neutral relay Fl and slow acting rela s SA and 813 all for a purpose to corresponding relays in the control .eld station includes a bank of stepping sing half-step relay VP and step- 7 22W, 31 and EX the latter being 11"1'1 is picked up on the last step for .-;-ols received at the associated station.

Compensating resistance CR is employed for the purpose of compensating for the line beyond a sending station, when this sending station conditions the line in towards the control ofiice for starting the system and for providing the lockout feature.

Change relay CH is provided to' register a change in any of the traflic controlling devices in the station or a change in the position of the track re ay, so that the system will be initiated for the transmission of indications. The operating circuits of this change relay have been omitted, but it will be understood that it re spends by means of a momentary deenergization its stick circuit, the manner in which this is accomplished being disclosed in Patent No. 1,852,402.

Lockout relay L6 is provided to determine when this held station is to transmit its indications. Whenever the lockout relay is picked up during a cycle for permitting the associated field station to transmit, the indication pulse is in-' immaterial to an understanding of the present invention and. may be as shown in the Hailes application, Ser. No. 82,711, filed June 1, 1936, now Patent No 2,114,001 granted April 12, 1938.

Impulse relay E cooperates with relay FP for the purpose of applying the indication impulses to the line circuit at the proper times, as will be explained in detail. Relay P33 and relay PT cooperate in providing the locking feature and in the following description it will be merely pointed out how these relays are controlled to initiate a cycle of operations from a transmitting field station. Indication transmitting relays P2 and N2 provide the positive and negativeimpulses for the indication code transmission, the functioning of these relays being explained in detail later.

Operation The system of the present invention is normally at rest and it may be initiated into a cycle of operations from the control office, when new controls are to be transmitted, or from a field station when new indications are to be transmitted. In. the event that new controls and new indications are ready to be transmitted at the same time at the beginning of a cycle, then the duplex feature f the system permits this transmission simultaneously during the same cycle.

For convenience in describing the operation of the present system, an operating cycle will be divided into a number of impulse periods sepafrom the terminal of battery LB in the control o-fiice, winding of relayF, back contact I6 of relay PC, front contact I! of relay NC, line conductor I2, through the tie at the end station illustrated by the dotted line in the upper right hand portion of Fig. 2A, line conductor IIB, back contact IIB of relay PB back contact II?' of relay FP back contact H8 of relay E back contact H9 of relay E back contact I I5 of relay FP winding of relay F line conductor Ill, front contact I8 of relay NC and back contact I?) of relay PC, to the terminal of battery LE1. It will be understood that the line circuit includes relays and contacts at other field stations in the system, similar to those traced for the field station illustrated in Fig. 2A.

Relay NC is normally energized over a circuit extending from back contact 23 of relay SB, back contact 24 of relay CF, back contact 25 of relay C and winding of relay NC, to The above described energizing circuit for the two-wire line circuit effects the energization of relays F, F and the line relays of all other stations connected to this line circuit. Since a potential is applied to line conductor I8, it will be assumed current flow effected by this polarity of energization of the line operates the polar contacts of the station line relays to the left, as illustrated by relay F of Fig. 2A.

At the field station, relay PT is normally energized over a circuit extending from contact I I I of relay F in its left hand position, back contact II 2 of relay SB and winding of relay PT to All other relays illustrated in the present drawings are normally deenergized, ex-

cept relay CH of Fig. 2A, which relay is responsive to a change in conditions at the associated field station for initiating the system for the transmission of indications.

Manual start.For the purpose of considering the operation of the present system for the transmission of controls, it will be asumed that the station illustrated in Figs. 2A and 2B is selected in response to the operation of the starting button STB of Fig. 1A. It will furthermore be assumed that switch machine lever SML is positioned to the right for controlling the operation of the track switch (not shown) at the illustrated station to its normal locked position.

The actuation of button STB effects the picking up of relays C and CD, after which a circuit is closed for picking up relay OC which extends from back contact 23 of relay SB, back contact 26 of relay CF, front contact 25 of relay C and winding of relay CC, to The opening of back contact 25 of relay C deenergizes the above described normal energizing circuit for relay NC, so that this relay is released.

A circuit is now closed for picking up relay PC which extends from back contact 25 of relay E, front contact 21 of relay 0C, front contact 28 of relay C, back contacts 29, 3B and SI of relays 3V, 2V and IV and winding of relay PC, to The release of relay NC opens the above described energizing circuit for the line and the picking up of relay PC again energizes the line circuit, but in this instance the current flow over the line circuit is of positive polarity and flows in a reversed direction from that above described. In other words, the energization of the line circuit is changed to a energization and this marks the beginning of the conditioning on period. This effects the momentary release of relay F in the control office and the immediate reenergization of this relay. This reversal of line circuit current also swings the polar -contacts of the F relays at the field stations from their left to their right hand positions.

Relay F? in the control office is energized over a circuit extending from front contact 32 of relay PC, front contact 33 of relay F and winding of relay FP, to Relay SA is energized over a circuit extending from front contact 32 of relay PC, front contact 3 of relay FP and winding of relay SA, to Relay SB is energized over a circuit extending from front contact 35 of relay SA and winding of relay SB, to A substitute circuit for that closed at front contact 32 of relay PC is now closed at front contact 38 of relay SB, for energizing relay SA during the on periods of the following cycle, irrespective of whether relay PC is picked up or not and for causing relay FP to repeat the operations of relay F.

The picking up of relay SB effects the energization of relay VP, over a circuit not shown and relay VP closes a first stick circuit for itself. The picking up of relay VP closes a circuit for energizing relay E which extends from front contact 3? of relay SB, back contacts 38, 39 and 40 of relays 3V, 2V and IV, front contact ll of relay VP and winding of relay E, to The picking up of relay E opens the above described circuit for relay PC at back contact 26, which allows relay PC to release and deenergize the line circuit to mark the end of the conditioning on period and the beginning of the first off period.

The deenergization of the line at the beginning of the first off period effects the deenergization of the F relays and relay FP is deenergized because of open front contact 33 of relay F. A second stick circuit is closed for maintaining relay VP energized, a pick up circuit is closed for picking up relay IV and the picking up of relay IV establishes a stick circuit for itself, which circuits are not shown. The picking up of relay IV opens the above described energizing circuit for relay E at back contact Ml, so that relay E releases and closes a pick up circuit for relay PC extending from back contact 26 of relay E, front contact 2! of relay OC, front contact 28 of relay C, back contacts 29 and 30 of relays 3V and 2V, front contact 3I of relay IV, front contact 42 of relay CD, jumper I3 in its full line position and winding of relay PC, to The picking up of relay PC applies a energization to the line circuit to mark the end of the first off period and the beginning of the first on period.

Relays F and FF respond as before and the picking up of relay FP effects the release of relay VP. A circuit is now closed for picking up relay E which extends from front contact 3'1 of relay SB, back contact 38 of relay 3V, back contact 39 of relay 2V, front contact 49 of relay IV, back contact ll of relay VP and winding of relay E, to Relay PC is now released because the above described energizing circuit for this relay is open at back contact 26 of relay E. This deenergizes the line to mark the end of the first on period and the beginning of the second off period.

Relays F and PP are released as before and relay 2V is picked up and stuck up. The picking up of relay 2V effects the release of relay E because of open back contact 39 and the release of relay E closes a pick up circuit for relay NC which extends from back contact 26 of relay E, front contacts 21 and 28 of relays 0C and C, back contact 29 of relay 3V, front con- 75 tact 30 of relay 2V, front contact 43 of relay CD, jumper M in its full line position and Winding of relay NC, to The picking up of relay NC applies a energization to the line circuit to mark the end of the second off period and the beginning of the second on period.

Relays F and FF are picked up as before and relay VP is picked up and stuck up in response to the piclnng up of relay FP. Relay E is now picked up over a circuit extending from front contact 31 of relay SB, back contact 38 of relay 3V, front contact 39 of relay 2V, front contact 4! of relay VP and winding of relay E, to The opening of back contact 26 of relay E effects the deenergization of relay NC, which in turn deenergizes the line circuit to mark the end of the second on period and the beginning of the third off period.

Relays F and FF are released as before, a second stick circuit is closed for maintaining relay VP energized and relay 3V is picked up. Relay E is now released because of open back con tact 38 and a circuit is closed for picking up relay PC which extends from back contact 26 of relay E, front contacts 2'! and 28 of relays 0C and C, front contact 29 of relay 3V, front contact it of relay CD, lever SML in its right hand position and winding of relay PC, to Relay PC applies a energization to the line circuit to mark the end of the third off period and the beginning of the third on period.

Relays F and FP are picked up as before and relay VP is released. A circuit is now closed for picking up relay E which extends from front contact 31 of relay SB, front contact 38 of relay 3V, back contact 4! of relay VP and winding of relay E, to The opening of back contact 26 of relay E deenergizes the above described circuit for relay PC, which effects the release of relay PC for deenergizing the line circuit to mark the end of the third on period and the beginning of the clearing out off period.

Relays F and PP are released as before, but since there is no other stepping relay to be picked up to change the condition of relay E, this latter relay remains energized and the line remains deenergized, with relays F and FF down, for a sufficiently long interval to release relay SA, because of open front contact 3 1 of relay ET. The release of relay SA effects the release of relay SB because of open front contact 35. The stick circuits for the stepping relays are deenergized by the release of relay SB and these stepping relays are released at this point in the cycle.v The opening of front contact El of relay {SB also effects the deenergization of relay E. Furthermore, the C and CD relays are deenergized by the release of relay SB.

Relay NC is now picked upover the previously described normal energizing circuit, which effects the normal energization of the line circuit for picking up relay F and for positioning the line relays at the stations to the left.

It will be understood that relay SA is not released during the above described impulsing of the line circuit, because front contact 34 of relay FP does not remain open for a sufficiently long period of time during this impulsing to allow relay SA to release. Relay 0C is likewise main- ..tained in its picked up position during the impulsingof the line circuit, because of a stick circuit extending from front contact 23 of relay SB, front contact 45 of relay E, front contact it and winding of relay CC, to When relay SB releases during the clearing out period,

the opening of its front contact 23 effects the deenergization of relay 0C for a time sufiicient to allow it to release. I

It will thus be seen that, in the event that impulsing is interfered with during the cycle, so that the system stops during an on period, relay E will remain down long enough to effect the release of relay 00, which in turn opens front contact 2'1! to effect the release of the PC or NC relay, so that the line is deenergized for clearing out the cycle. In the" event that the system stops in an off period, then the line is deenergized sufficiently long for relay Fl? to remain down sufliciently long to effect the releasev of relay SA, so that the system is cleared out.

Polarity selection of impulses.--In the above example, it has been pointed out how relay PC is picked up during the conditioning on period, the first on period and the third on period and how relay NC is picked up during the second "on period. Relay PC is always picked up during the conditioning on period for energizing the line with a impulse and the succeeding impulses are rendered or in accordance with the positions of the code jumpers and the control levers associated with relay CD.

In the event that jumper I3 is in its alternate dotted line position, then relay NC is picked up during the first off period-for making the first on impulse instead of as in the above example. The same applies to jumper M, which is selected when relay 2V is picked up during the second off period for selectively energizing relay PC or NC to render the second on impulse or This operation occurs on each step of the cycle for determining the code to be applied to the line circuit, by selecting the PC or NC relay during off periods in readiness for energizing the line with a or impulse during succeeding on periods, in accordance with this selection.

It will-be understood that this arrangement may be extended for as many steps as desired, with stepping relays being picked up during the off periods and the VP relay being shifted from one position to another during the on periods. The stepping relay r operation at the field stations is the same as in the control office,

these station stepping relays being picked up I and released in approximate synchronism, with corresponding relays in the office. The circuit arrangement for the stepping relay operation at the station is merely indicated by dotted line H20.

It will be noted that the pick up circuit for relay FP extends through front contact N3 of relay L0 or front contact N4 of relay S0 so that the operation of relay FP at afield station is dependent on a station being selected for controls by its SO relay being picked up, or that the station is transmitting indications by reason of its LO relay being picked up. The actuation of the contacts of relay F to the right during the conditioning "on period effects the picking up of relay S0 over a circuit not shown, after which relay FP is energizedover a circuit ex tending from contact ill of relay F in its right hand dotted position, back contact N3 of relay L0 front contact N4 of relay S0 back contact $23 of relay E and winding of-relay PPkto A stick circuit for relay FP is established at its front contact 24, which circuit bridges back contact I23 of relay E and is for the purpose of maintaining relay FP energized until relay F is deenergized, irrespective of the position of relay E Relay SA is picked up during the conditioning on period, over a circuit first closed at contact III of relay F in its right hand dotted position and thereafter closed at front contact I25 of relay FP Relay SA closes a circuit for picking up relay SB which extends from front contact I26 of relay SA back contact I21 of relay PB and winding of relay SE to Relay VP is picked up during the conditioning on period, is released during the first on period, is picked up during the second on period and is released during the third on period, in approximate synchronism with the VP relay in the office.

The picking up of relay VP during the conditioning on period closes a circuit for picking up relay E which extends from front contact I28 of relay 5B back contacts I29, I30 and I 3| of relays 3V 2V and IV front contact I32 of relay VP and winding of relay E to When relay IV is picked up during the first off period, the above described circuit for relay E is opened at back contact I3I and relay E is released. When relay VP releases during the first on period, the circuit for relay E is again completed by way of front contact I3I of relay IV and back contact I32 of relay VP The picking up of relay 2V in the second period opens the energizing circuit for relay E at back contact I39. The picking up of relay VP during the second on period completes the energizing circuit for relay E at front contact I32. The release of relay VP during the third on period completes the energizing circuit for relay E by way of front contact I29 of relay 3V and back contact I32 of relay VP When relay FP remains down for an extra long interval during'the clearang out period, the continued open condition of front contact I25 effects the release of relay SA and the open condition of contact I26 effects the release of relay SE Relays S0 E and the stepping relays are all deenergized by the release of relay SE The picking up of relay F'P during the conditioning on period changes the path of the line circuit, from that previously described, to one which may be traced from line conductor I 0, winding of relay F front contacts H and II! of relay FF and back contact I I6 of relay PB This change in the line circuit path is for no purpose during a control cycle, but its function will be described in connection with an indication cycle. Furthermore, relay PT is released during the conditioning on period, by the opening of back contact II2 of relay SB and relay PT is not again reenergized until relay SE is released during the clearing out period and relay F closes contact III in its left hand position during the normal period. The purpose of relay PT will be described in connection with the starting of an indication cycle.

Control coda-When controls are transmitted, field stations are selected one at a time in accordance with the combination of and impulses applied to the line circuit during the station selection part of the cycle, which in the present embodiment is assumed to be during the first and second on periods, as determined by the positions of jumpers I3 and I4 of Fig. 1A. The circuits for the field stations are similar, the difference being in thepositions of the station code jumpers (not shown) which serve to condition selecting circuits for the SO relays, so that only one of these relays will remain energized after the receipt of the last station selecting code impulse. As above mentioned, it is believed unnecessary to illustrate the detailed arrangement for accomplishing station selection.

After the proper combination is applied to the line circuit for selecting the desired station, then the following impulses in the line circuit are for the purpose of controlling switch machines, signals and the like, in accordance with the position of the control levers in the ofiice associated with the selected station. With lever SML in its right hand position, a impulse is applied to the line circuit during the third on and the actuation of contact I 33 of relay'E to the right, in response to this impulse, is effective to control a switch machine control relay which may be connected to the No. 3 control channel, the circuit being traced from front contact I34 of relay S0 back contact I35 of relay E front contact I36 of relay FP contact I33 of relay FP in its right hand dotted position, front contact I31 of relay 3V and by way of the No. 3 channel conductor, to the control relay connected to this conductor. In the event that lever SML is in its left hand dotted position, then the third on impulse is for positioning contact I33 of relay F to the left, which selects the No. 3 channel conductor, for controlling the switch machine control relay to its opposite position.

In a similar manner, any number of additional steps may be provided for transmitting additional controls to the selected field station for governing signals and such other devices as may be employed. It will be noted that the and control channel circuits can only be energized at a station where relay S0 has its front contact I34 closed, which effects the selection of the desired station, so that these control channel conductors cannot be energized during a cycle in which the SO relays are dropped out. The purpose of back contact I38 of relay SE is to provide an energizing circuit for picking up relay S0 when relay F swings to the right, this circuit extending through back contacts I31, I39 and I40 of relays 3V 2V and I V An executing bus has been illustrated, which is for the purpose of executing the composite control code at a selected station, after this code has been registered and the system is going through its clearing out period. This circuit extends from front contact I4! of relay S0 (up until relay SE releases), back contact I42 of relay SA (down for an appreciable interval of time before relay SB releases) and front contact I43 of relay EX this latter relay being released after the release of relay SE the same as the stepping relays.

Transmission of indications.Although the system is of the coded duplex type, arranged for the transmission of indications from any station to the control ofl'ice during the same cycle that controls are transmitted to the same station or to some other station, it will first be explained how he system operates for the transmission of indications alone on a separate operating cycle. The duplex feature of the system will be explained later on in the description. It will now be assumed that the station illustrated in Figs. 2A and 23 has indications ready for transmission to the control ofiice.

Automatic start.A change in the condition of the track section or a change in the condition of the trafiic controlling devices at the illustrated station effect the deenergization of relay CH which closes a circuit for picking up relay PB extending from back contact I44 of relay SE back contact [36 of relay FP contact I33 of relay F in its left hand position, back contacts M5, M5 and M! of relays 3V 2V and W back contact 548 of relay CH back contact MS of relay L front contact l5b of relay PT back contact 15! of relay FE and winding of relay PB to Relay PB closes a stick circuit for itself extending from front contact I52 of relay PT front contact 953 and winding of relay FB to The picking up of relay PB opens the above described normally energized line circuit at back contact H6, which effects the release of relays F F and all other line relays at other stations in the system. The opening of contact ill of relay F deenergizes relay PT and, after a cornparatively long interval of time, relay PT releases.

The release of relay F in the control office and the consequent closing of its back contact i5 is effective to pick up relay CF. Relay 0C is now picked up over a circuit extending from back contact 23 of relay SB, front contact 2% of relay CF and winding of relay CC, to The opening of back contact 2d of relay CF deenergizes relay NC, to remove the energization from the line circuit and the picking up of relays CF and 00 close a circuit for picking up relay PC, to apply a energization to the line circuit. The pick up circuit for relay PC extends from (-I-), back contact 26 of relay E, front contact 2"! of relay 00, back contact 28 of relay 0, front contact ll of relay CF, back contact at of relay 9V and winding of relay PC, to The line is closed at the station at front contact i it of relay PB back contact 686 of relay PT back contact Q8? of relay SB and resistance CR This energization of the line circuit picks up relay F in the control office and positions relay F at the field station to the right. This energization is held on the line for a comparatively long interval of time, during which conditioning takes place at the office and at the stations in the same manner described in connection with a control cycle. In this instance, the actuation of contact l33 of relay F to the right effects the picking up of relay S0 as before, but during the succeeding cycle relay S0 is released because the impulses applied to the line circuit are all (for a reason to be described), which makes up a phantom code ineffective to select any field station. Contact 33 to the right also picks up relay L0 by way of back contact 553 of relay W by means of a circuit not shown, but which circuit is dependent on relay PB being picked up,

- due to the initiation of the system from the illustrated field station.

As previously mentioned, the lookout feature of the present system is not shown, since this feature is immaterial to an understanding of the present invention and since it may be the same as disclosed in the above mentioned Hailes application. It need only be understood that relay L0 at the illustrated station is picked up and stuck up throughout the following cycle, when indications are initiated at the station. Furthermore, when indications are simultaneously initiated at two or morestations, the LO relay at the station nearest the control ofiice will remain up during the succeeding cycle, while the other LO relays which were picked up will be released during the conditioning on period.

During an indication cycle, the line circuit is impulsed with a series of impulses, the stepping relay banks and the E relays being operated in the same manner described. in connection with a control cycle. Relay NC is selected and'energized each time back contact 26 of relay E closes, over a circuit extending through front contact 2! of relay ()0, back contact 28 of relay C, front contact ll of relay CF and front contact 36 of relay IV, the latter relay being picked up during the first off period following the conditioning on period,'during which the line was energized with a impulse.

Registration of a field statio .-Recalling that the twowire line circuit is impulsed with a series of impulses from battery LB in the control office, by the intermittent energization and deenergization of relay NC, controlled by relay E, which is in turn controlled by the response of the stepping relay bank to these impulses, it will now be explained how the transmitting field station inserts an indication impulser into the line circuit, during the above described 0 periods,

for providing indication codes made up of or zero impulses in the line.

At the particular station (assumed to be the station illustrated in Figs. 2A and 213) having indications to transmit, lockout relay L0 is maintained energized throughout the cycle. Recalling that the stepping relay bank in the control office operates in synchronism with the stepping relay banks at the field stations, it will benoted that the closure of front contacts I54 and I55 (see Fig. 2B) of relay L0 permits the energization or deenergization of relays N2 and P2 in accordance with a code combination made up by thepositions of the indication code jumpers and the positions of indication transmitting contacts on certain relays, such as relay WP When relay SE is picked up during the condi- The opening of front contact E52 of relay PT opens the stick circuit of relay PB this latter relay having its stick circuit maintained closed also by way of front contact I55 of relay L0 and back contact It'll of relay $0 for a purpose which relates to the lockout feature. With the stick circult of relay PB open at front contact I52 of relay PT and at back contact it! of relay S0 relay P3 is released because its pick up circuit is open at front contact E5!) of relay PT. This release of relay PB re-establishes the line circuit hrough all stations to the end of the line, as will be noted by tracing the circuit for line wire it! through relay F back contacts H5, H9, H8 and H! of relays FP and E and back contact lid of relay P33 to line conductor Ill), which line conductor is tied to the return conductor 52 at the end station.

The line circuit is impulsed with the indication I code impulses during the off periods, while relay FP is down and relay E isup. At this time relay F is short-circuited by means of back contact i593 of relay FE" and front contact I59 of relay E so that the indication impulses applied to the line circuit are ineffective to operate the line relay which controls stepping. At all other stations at which stepping takes place, for example, during a duplex cycle when controls are being transmitted, a similar circuit is effective to shortcircuit the line. relays at these stations to prevent stepping during the transmission of indication impulses. Likewise, in the control office, relay E is picked up and relay F is released during these off periods, so that a bridge is placed across the line in the control office extending from conductor Ill, front contacts 49 of relay E, back contacts 51! and 5f of relays NM and PM, winding of relay R, back contact '52 of relay F, back contacts 53 and 5 3 of relays PC and NC, to conductor I0. It will thus be seen that, during the off periods, relay R in the control office is momentarily substituted for relay F in the line.

In the example chosen for illustration, the first off period is not impulsed, in other words, the indication code provided during the first off period is a zero impulse. This is because code jumpers I 65 and I BI (Fig. 2B) are both disconnected from so that neither relay NZ nor relay PZ is picked up and the line is not energized from the station during the first off" period. During the first on period, a circuit is closed for picking up relay PZ which extends from jumper I62, front contact I63 of relay IV back contacts I64 and I65 of relays 2V and 3V front contact I55 of relay L0 front contact I68 of relay FF and winding of relay PZ to When relay E is picked up during the first on period, a first stick circuit is closed for relay PZ extending from front contact I51 of relay L0 front contact I68 of relay PZ front contact I69 of relay E and winding of relay PZ to When relay FP releases during the second off period, a second stick circuit is closed for relay PZ by reason of back contact I56 bridging front contact I69. It will thus be seen that, when relay PZ is picked up during the first on period, it is stuck up throughout the next (second) off period and until relay FP is picked up in the next succeeding (second) on period.

With relay P2 picked up throughout the second off period, a impulse is applied to the line circuit during the interval between the dropping of relay FF and the dropping of relay E over a circuit which may be traced from the terminal of battery LB back contact I 18 of relay N2 front contact H! of relay PZ front contact N3 of relay E back contact IE1 of relay FP back contact I N3 of relay PfB line conductor I I0, through the tie at the end station, line conductor 52, front contact 49 of relay E, back contacts 50 and EI of relays NM and PM, winding of relay R, back contact 52 of relay F, back contacts 53 and 54 of relays PC and NC, line conductor I0, back contact 558 of relay FP front contact I59 of relay E back contact I I5 of relay FP front contact I IQ of relay E front contact I12 of relay SE front contact I13 of relay PZ, back contact I1 l of relay NZ and front contact I15 of relay L0 to the terminal of battery LB The above described circuit, including the line conductors, extends through other stations connected to the system and in order to provide a path through these stations, back contact I16 of relay L0 is provided, it being understood that similar back contacts are provided on the lookout relays at the other stations. The reason for this will be apparent when considering that the FP, E and SB relays at the other stations operate in approximate synchronism with those at the transmitting station, so that the path extending through back contacts of the FP relay and front contacts of the E relay at the transmitting station, by way of back contact I I5 of relay PB will find a path over conductor I ill which is similar to that extending through back contact I58, front contact I59, back contact H5, front contact H9, front contact I12, back contact I16, front contact II8, back contact H1 and back contact IIB, to the'line conductor extending toward the end of the system.

From the above description it will be observed that the contact arrangement shown on relays FP and E in the upper left hand portion of Fig. 2A, connects and disconnects the indication impulser to and from the line circuit during the off periods and that the contact arrangement, including contact I15 of relay L0 closes the line circuit around contacts 110, I1I, I13 and I14 of relays PZ and NZ at the stations not sending indication impulses.

The impulse applied to the line circuit, during the second off period, is effective to position relay R in the control oflice to the right for picking up relay PM, by means of a circuit closed at contact 55 of relay R, in its right hand dotted position. This impulse is only momentary, it being terminated by the picking up of relay PM and the consequent opening of its back contact 5 I,

,as well as the releasing of relay E at the transmitting station and the consequent opening of the impulser circuit at front contacts I I8 and I IS. A stick circuit is provided for relay PM which extends from front contact 56 of relay SA, back contact 51 of relay F, front contact 58 and Winding of relay PM, to This stick circuit is maintained as long as relay F is down and as long as relay E is down, because of back contact 59 of 1;,

relay E bridging back contact 51 of relay F. Relay PM is therefore stuck up throughout the second on period, until relay E picks up and opens its back contact 59, whereupon relay PM is released.

It will be understood that a impulse may be applied to the line circuit during the second ofi period, by connecting jumper I62 in its dotted line position and jumper I11 in its full line position, so that relay PZ will not pick up 11'- and relay NZ will pick up. The method of making this impulse will be understood in connection with the transmission during the third off period, later to be explained.

Execution of the indication codes transmitted during the oil periods is effected during the following on periods. In the above example, a zero impulse was transmitted during the first off period, so that neither relay PM nor NM was picked up. This condition is executed while relay E is down, by closing a circuit to the first Zero indication channel extending from front contact 60 of relay CF, back contacts SI, 62 and 63 of relays PM, NM and E, back contacts 64 and 65 of relays 3V and 2V and front contact when execution takes place, by means of a circuit extending from front contact 69 of relay CF, front contact 10 of relay PM, back contacts H and 12 of relays NM and E, back contact 13 of relay 3V and front contact 14 of relay 2V, to channel conductor 68, for operating pilot relays 3PT and 4PT in a manner analogous to the operation of relays IIR and HR later to be explained.

Although not illustrated, it will be readily understood that two pilot relays provided for each step and operated in response to any one of the three code combinations per step, may be used to select any one of eight station relays for the two steps, the ninth possible code combination being a phantom code not used, due to the fact that when controls alone are transmitted over the sys-,

tern, the indication code, comprising a zero impulse at each step, is inherently transmitted.

Thus, relay 8ST is assumedto correspond to the illustrated field station and to be picked up in response to the above described indication code transmitted in accordance with the positions of jumpers I6, Nil, IE2 and I'll, to register or identify in the control office, that the field station of Figs. 2A and 2B is the transmitting station.

Transmission of indications.Relay WP of Fig. 2B has been provided to illustrate how a choice of one out of three indications may be transmitted at a particular step of the cycle and this step in the present embodiment is assumed to be the third off period, asselected by the picking up of relay lV during the second off period and completed by the picking'up of relay FP during the second on period.

With relay WP in the illustrated position, a circuit is closed for picking up relay NZ during the second on period extending from front contact N8 of relay WP polar contact N9 of relay WP in its left hand position, front contact 223 of relay2V back contact 18! of relay 3V front contact 154% of relay L0 front contact I82 of relay F and winding of relay N2 to Relay NZ is stuck up, as long as relay E is picked up during the'third off period, over a circuit extending from front contact it of relay L0 front contact 885 of relay NZ front contact I25 of relay E and winding of relay N2 to The release of relay FP completes the stick circuit for relay NZ at back contact I82 before relay E releases, so that relayNZ is stuck up until relay FP is picked up during the third on period. This means that relay NZ will be maintained in its picked up position throughout the third oif period and released in the next (third) selection.

With relay NZ up throughout the third on period, a impulse is momentarily applied to the line circuit over the previously described cir-' cult, but which nowextends through front contacts H8 and H4 of relay NZ and back contacts Ill and H3 of relay PZ This indication impulse, applied to the line circuit during the third off period, is effective to position relay R to the left for picking up relay NM over a circuit extending through contact 55 of relay R in its left hand dotted position. Relay- NM immediately opens the line circuit at back contact 50, but establishes a stick circuit for itself before contact 55 opens, which stick circuit ex.- tends from front contact '56 of relay SA, back contact 51 of relay F, front contact 15 and winding of relay to Contact 51 is bridged by back contact 56 of relay E, to maintain relay NM stuck up until relay E is picked up during the third on period.

The'third indication code is executed during the third on period by closing a circuit extending from front contact 16 of relay CF, back contact ll of relay PM, front contact 18 of relay NM, back contact 79 of relay E, front contact of relay 3V, front contact lll of relay 8ST, lower winding of relay IIR and lower winding of relay 213., to As indicated by the arrows associated with the IR relays, current through the lower windings of relays HR and HR. positions on period, in readiness for the next cations.

lamp NL is an indication that relay WP is repeating the associated track switch in its normal locked positon.

In the event that contact I19 of relay WP is in its reverse dotted line position, then relay PZ would be picked up during the second on period, for applying a indication impulse to the line circuit during the third off period, which would be effective to pick up relay PM and leave relay NM down. Whenthis condition is executed, a circuit is closed through front contacts 69 and it of relays CF and PM, back contacts H and 12 of relays NM and E, front contact 13 of relay 3V, front contact 8d of relay 8ST, upper winding of relays SIR and lower winding of relay HR in serice, to The arrows associated with these windings indicate that polar contact 83 of relay SIR is positioned to the right and polar contact 32 of relay 21B is positioned to the left, which is effective to close a circuit for lighting lamp RL, as an indication thatrelay WP is in its reverse switch indicating position.

In the event that neutral contact I18 of relay WP is open, then neither relay PZ nor NZ will be picked up, so that a zero indication impulse is transmitted during the third off period, which is effective to leave relays PM and-NM both down during the third on period, when this condition is executed. A circuit is then completed by way offront contact 69 of relay CF,

back contacts 6!, B2 and 6 3 of relays PM, NM and front contact 54 of relay 3V, front contact of relay EST and upper winding of relay HR, to As illustrated by the arrow, thispositions polar contact 82 to the right so that neither lamp is energized, as an indication that relay WP is repeating the track switch in its unlocked condition. I v

From the above explanation of the operation of relays HR and 21R, it, is believed clear that similar relays provided for the first two steps may be operated in any one of three distinctive the above mentioned station selection feature may be provided to a particular ST relay, in accordance with the station transmitting its indi- Duplex operation-It has been pointed out that control and indicationcycles may each occur separately or simultaneously. The operations for a control cycle alone and the operations for an indication cycle alone have been described and it will now be briefly explained how the system operates when controls and indications are transmitted during the same cycle,

The actuation of a starting button in the control ofiice can pick up its associated CD relay while the system is at rest and relay C will be picked up to mark the cycle as one during which controls are transmitted. A field stationmay initiate the system while it is at rest or during the initiation from the control office, so that its lockout'relay may be picked up at the beginning of a cycle and maintained picked up throughout the succeeding cycle.

Therefore, under the'condition that thesystem is initiated by the picking up ofa CD lay in the ofiice and a lockout relay atpa field station at the beginning of a cycle, both controls and indications can be transmitted during this cycle. The polarity of each control impulse transmitted over the line during the above described fon periods, is determined by the code jumper and lever connections selected by the energized 'CD relay. The identification or regis-.

. positions for each step in combination, so that tration of a particular field station for the transmission of indications is determined by the particular lockout relay which is picked up, for effecting the transmission of or zero impulses during the 01f periods, as determined by the connections of the code jumpers at the field station. Furthermore, indications from the registered station are transmitted during the steps following station identification by providing or zero impulses during the ofi periods, all as previously described. Since controls are transmitted outward from the ofiice and sinceindications are transmitted-inward to the ofiice by the separate and independent conditioning of the two-wire line circuit, these controls and indications can be simultaneously transmitted during the same cycle.

The clearing out operation for an indication cycle or for a duplex cycle is the same as previously described in connection with a control cycle and need not be repeated.

Although one specific embodiment of the invention has been shown, it is to be understood that various rearrangements may be made and still come within the scope of the invention.

Having thus described a centralized traflic controlling system as one embodiment of the present invention, it is desired to be understood that this form is selected to facilitate in the disclosure rather than to limit the number of forms which the invention may assume and it is fluther to be understood that various modifications adaptations and alterations may be applied to the specific form shown to meet the requirements of practice without in any manner departing from the spirit or scope of the invention except as limited by the appended claims.

What I claim is:

1. In a remote control system; a control ofiice and a field station connected by a line circuit; a first and a polar line relay in said ofiice selec tively and individually connected in series with said line circuit; means including said first line relay for impressing a series of control impulses on said line circuit for synchronously marking off a series of successive time spaced impulse periods at said oflice and at said station and for excluding said first line relay from said line circuit during each time space; means for connecting said polar line relay in series with said line circuit during the time spaces between the im pulse periods; a code transmitter at said station; means for causing said code transmitter to apply a positive, a negative or a zero current impulse to said line circuit during each of the time spaces between said impulse periods, whereby codes are transmitted over said line circuit and said polar line relay is operated or left unoperated during each time space; and means controlled by said polar line relay for registering said codes.

2. In a remote control system; a control office and a field station connected by a line circuit; a first and a polar line relay in said office selectively and individually connected in series with said line circuit; means including said first line relay for impressing a series of distinctive polarity control impulses on said line circuit at said ofiice for synchronously marking off a series of successive time spaced impulse periods at said ofice and at said station and for characterizing a control code by the polarity pattern of such series of impulses, said means also excluding said first line relay from said line circuit during each time space'means controlled by said first line relay for connecting said polar line relay in series with-said line circuit during the time spaces between the impulse periods; a code transmitter at said station; means for causing said code transmitter to apply impulses of positive, negative, and zero current to said line circuit during the time spaces between said impulse periods, whereby codes are transmitted over said line circuit and said polar line relay is operated to a particular polar position or is left unoperated during each time space; and means controlled by said polar line relay for registering said codes.

3. In a remote control system; a control office and a field station connected by a line circuit; a first and a polar line relay in said oflice selectively and individually connected in series with said line circuit; means including said first line relay for impressing a series of distinctive polarity control impulses on said line circuit to form a polarity pattern to constitute a code and for synchronously marking off a series of successive time spaced impulse periods at said office and at said station, said means also excluding said first line relay from said line circuit during each time space; means controlled by said first line relay for connecting said polar line relay in series with said line circuit during the time spaces between the impulse periods; a code transmitter at said station; means for causing said code transmitter to apply positive, negative and zero current impulses to said line circuit during the time spaces between said impulse periods, whereby codes are transmitted over said line circuit and said polar line relay is left unoperated or is distinctively operated once during each time space thereby; means controlled by said polar line relay for registering said codes, and means controlled by said polar line relay for removing itself from said line circuit.

4. In a remote control system; a control office and a plurality of field stations connected by a line circuit; a first and a polar line relay in said ofiice selectively connected in series with said line circuit; means including said first line re lay for intermittently energizing said line circuit from a source of current in said office to synchronously mark off a series ofsuccessive time spaced impulse periods at said ofiice and at said stations and for excluding said first line relay from said line circuit during each time space; means for connecting said polar line relay in said line circuit during the time spaces between said impulse periods; a code transmitter at each of said stations; means for causing the code transmitter at a transmitting station to insert itself in series with said line circuit and apply positive, negative and zerov current impulses thereto during the time spaces between said impulse periods, whereby codes are transmitted over said line circuit and said polar line relay is operated or left unoperated for each impulse thereby; means controlled by said polar line relay for registering said codes; and means at each non-transmitting station for preventing the insertion of the associated code transmitter.

5. In a remote'control system; a control oifice and a. plurality of field stations connected by a line circuit; a first and a polar line relay in said ofiice selectively connected in series with said line circuit; means including said first line relay for intermittently energizing said line circuit from a source of current in said office to synchronously mark off a series of successive time spaced impulse periods at said oifice and at said stations and for excluding said first line relay from said line circuitduring each time space; means for connecting said polar line relay to said line circuit during the time spaces between said impulse periods; a code transmitter at each of said stations; means for causing the code transmitter at a transmitting station to insert itself in series with said line circuit and apply polar and zero current impulses thereto during the time spaces between said impulse periods, whereby codes are transmitted over said line circuit and said polar line relay is reversibly operated or left unoperated during each time space thereby; means controlled by said polar line relay for registering said codes; and means at each nontransmitting station for preventing the insertion of the associated code transmitter.

'6. In a remote control system, a control omce and a plurality of field stations connected by a line circuit; a first and a polar line relay in said ofiice selectively connected in series with said line circuit; means located wholly at said ofiice and including said firstline relay for intermittently energizing said line circuit from a source of current in said oflice to synchronously mark ofi a series of successive time spaced impulse periods at said omce and at said stations; mean's for disconnecting said first line relay from and connecting said polar line relay to said line circuit during each time space between said impulse periods; a code transmitter at each of said stations; means for causing the code transmitter at a transmitting station to intermittently insert itself in series with said line circuit and apply polar and zero current impulses thereto during the time spaces between said impulse periods, whereby codes are transmitted over said line circuit and said polar line relay is intermittently reversibly operated or left unoperated thereby; means controlled by said polar line relay for registering said codes; and means at each nontransmitting station for preventing the insertion of the associated code transmitter in said line circuit, whereby said line circuit is rendered continuous through all of said plurality of stations during both the impulse and the time space of an impulse period.

7. In a remote control system; a control office and a plurality of field stations connected by a line circuit; a first line relay and a polarity responsive second line relay in said ofiice selectively connected in series with said line circuit; a station line relay at each of said stations connected in series with said line circuit; means including said first line relay for intermittently energizing said line circuit from a source of current in said office to synchronously mark off a series of successive time spaced impulse periods at said oflice and at said stations; means for disconnecting said first line relay from and connecting said second line relay to said line circuit during the time spaces between said impulse periods; a code transmitter at each of said stations; means including the station line relay at a transmitting station for causing the code transmitter at that station to insert itself in series with said line circuit and apply polar impulses thereto during the time spaces between said impulse periods, whereby codes are transmitted over said line circuit and said polarity responsive second line relay is reversibly operated thereby; means controlled by the operation of said polarity responsive second line relay for registering said codes; means at each non-transmitting station for preventing the insertion of the associated code transmitter in said line circuit whereby said line circuit is rendered continuous through all of said plurality of stations; and means for removing each station line relay from the line when a code transmitter isinserted in the line circuit at a transmitting station.

.3. A communication system for transmitting control codes from an oifice to any one of a plurality of stations and for transmitting indication codes from any one of said stations to said office comprising, a single line circuit extending from said ofiice through all of said stations, a line relay at said office and a polar line relay at each of said stationsincluded in series in said line circuit, a polar indication line relay at said office, means at said ofiice for energizing said line circuit extending through all of said line relays by series of positive and negative polarity control impulses arranged in a polarity pattern to define a code,

step-by-step mechanism at said office and at each of said stations controlled solely by said impulses irrespective of their polarity, means at each field station controlled by the polar line relay at such station and the step-by-step mechanism at such station responsive to such series of impulses provided the impulses form a polarity code pattern corresponding to that station, means at said ofiice controlled by the step-by-step mechanism at said office for disconnecting the line relay at said ofiice from said line circuit and connecting said polar indication line relay in series in said line circuit during the time spaces between said impulses, indication transmitting means at a particular station for transmitting an indication impulse of distinctive polarity from such station to said office for each time space when said indication line relay is included insaid line circuit, and indication means in said oflice responsive to the repeated operation of said indication relay if the code pattern of the particular series of indication impulses corresponds to the code for said indication means.

9. A communication system for transmitting control codes from an ofiice to any one of a plurality of stations and for transmitting indication codes from any one of said stations to said ofiice during the same cycle of impulses comprising, a single line circuit extending from said office through all of said stations, a line relayat said office and a polar line relay at eachof said stations included in series in said line circuit, a polar indication line relay at said ofiice, means at said ofiice for energizing said line circuit extending through all of said line relays by series of positive and negative polarity control impulses arranged in a pattern to define a polarity code, stefi-by-step mechanism at said ofiice and at each of said stations controlled solely by said impulses irrespective of their polarity, means at each field station controlled by the polar line relay at such station and the step-by-step mechanism at such station responsive to such series of impulses provided the impulses form a polarity code pattern corresponding to that station, means at said ofiice controlled by the step-by-step mechanism at said oflice for disconnecting the line relay at said olfice from said line circuit and connecting said polar indication line relay in series in said line circuit during the time spaces between said impulses, indication transmitting means at a particular station for transmitting an indication impulse of distinctive polarity from such station to said office for each time space when said indication line relay is included in said line circuit, indication means in said ofiice responsive to the repeated operation of said indication relay if the code pattern of the particular series of indication impulses corresponds to the code for said indication means, and lock-out means for allowing the indication transmitting means at only one of said stations to transmit indication impulses during a particular series of control impulses.

10. A communication system for transmitting controls from an ofiice and transmitting indications from a field station during the same series of control impulses comprising, an ofiice and a plurality of field stations, a single line circuit connecting said office and all of said field stations, a line relay at said oflice and a polar line relay at each of said field stations normally all connected in series, step-by-step mechanism at said office and at each of said stations controlled by its respective line relay, means at said office for applying a series of distinctive polarity control impulses on said line circuit to operate said polar line relays to distinctive positions and to.

operate said step-by-step mechanisms, code responsive means at each field station controlled in accordance with the polar positions assumed by its associated polar line relay on a plurality of steps, an indication line relay in said office, means controlled by the step-by-step means for excluding said ofiice line relay from and including said indication line relay in said line circuit during each time space between successive impulses, indication transmitting means at each field station for applying an indication potential on said line circuit for each time space to operate said indication line relay, and locking means at each of said stations which are interlocked to render only one of said indication transmitting means effective at one time.

11. In a remote control system, a control oflice and a plurality of field stations connected by a line circuit, means including a first source of direct current in said ofiice for intermittently energizing said line circuit with a series of time spaced direct current impulses, step-by-step mechanism at said ofiice and at each of said stations operable in synchronism by said time spaced impulses, a second source of direct current at each of said stations, means at each of saidstations effective during each time space to prevent the step-by-step mechanism at such station from being controlled by an impulse on said line 'circuit and for selectively connecting the associated second source of direct current to said line circuit in normal or reverse direction or to leave said second source of direct current disconnected to form a plurality of code characters one character for each time space, means at said control ofiice efiective to disconnect said first source of current and said ofiice step-by-step mechanism from said line circuit during each time space; and means at said control ofiice connected to said line circuit only during said time spaces and controlled by said code characters for registering a separate one of said stations in said control office.

WILLIAM D. HAILES. 

